Hello dear, thanks for your question on HCM. Nocturnal hypoxia can be seen in 1. Obstructive sleep apnoea (OSA) 2. COPD (Chronic Obstructive Pulmonary Disease ) 3. CCF (congestive cardiac failure) etc So better to consult pulmonologist and get done polysomnography (sleep study) first. Chances of OSA are high. If this is normal than get done chest x ray and PFT ( PULMONARY FUNCTION TEST ) to rule out COPD. Get done 2D Echo to rule out CCF. In my opinion sleep study will clearly indicate if hypoxia is present or not. So consult pulmonologist and discuss all these.